A method for producing a conjugated diene, such as butadiene, etc., through a catalytic oxidative dehydrogenation reaction of a monoolefin, such as n-butene, etc., has hitherto been known. In addition, various investigations regarding the separation of a high boiling point by-product in a formed gas have also been made.
For example, Patent Document 1 discloses an invention in which a minute amount of a high boiling point by-product contained in a product gas is introduced into a quench column (cooling column) in which a wall surface temperature within the column is kept at a specified temperature and brought into contact with spray water to separate the high boiling point by-product.
Patent Document 2 discloses a method in which a reaction product gas is introduced into a quench column (cooling column), and an alkaline substance is poured into cold water to be supplied into the column top of the quench column, thereby dissolving a high boiling point by-product composed mainly of an organic acid in an aqueous phase to remove it.
Patent Document 3 discloses a method in which a reaction product gas is introduced into a quench column (cooling column), and a sublimable high boiling point reaction by-product is removed by using, as a quenching agent (cooling agent), an organic amine aqueous solution or an aromatic organic solvent.
Patent Document 4 discloses a production method of using a circulating liquid containing an alkaline compound by using a quench column in which a cooling step of a reaction product gas has two or more zones. Patent Document 5 discloses a method in which a reaction product gas is preliminarily cooled and then supplied into a quench column (cooling column). Patent Document 6 discloses a method in which a column bottom liquid of a cooling column is subjected to swirling fluidization along a wall surface of the cooling column.